Stockholders' deficit - Warrants Outstanding (Details) - Warrants - $ / shares	6 Months Ended	12 Months Ended
Jun. 30, 2018	Dec. 31, 2017
Beginning balance, warrants	49,504,075	19,637,409
Beginning balance, warrants exercise price	$ 0.0690	$ 0.03
Warrants Granted, shares	33,083,333	29,866,666
Warrants granted, price	$ 0.11	$ 0.0945
Ending Balance, warrants	82,587,408	49,504,075
Ending Balance, warrants exercise price	$ 0.0850	$ 0.0690

Exercise price per share or per unit of warrants or rights outstanding.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 235
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.4-08.(i)(4))
-URI http://asc.fasb.org/extlink&oid=26873400&loc=d3e23780-122690

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- Definition

Number of warrants or rights outstanding.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 235
-SubTopic 10
-Section S99
-Paragraph 1
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-URI http://asc.fasb.org/extlink&oid=26873400&loc=d3e23780-122690

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- Definition

The weighted average fair value at grant date for nonvested equity-based awards issued during the period on other than stock (or unit) option plans (for example, phantom stock or unit plan, stock or unit appreciation rights plan, performance target plan).

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
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-URI http://asc.fasb.org/extlink&oid=109197908&loc=d3e5070-113901

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- Definition

Net number of non-option equity instruments granted to participants.

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-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
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